王秋良1，嚴(yán)陸光1
( 1. 中國(guó)科學(xué)院 電工研究所， 北京 100080；
2. 上海大學(xué) 材料科學(xué)與工程學(xué)院， 上海 200072)
摘 要: 在Bi-6%Mn合金從高于355℃(升溫過(guò)程中MnBi化合物磁性轉(zhuǎn)變溫度)的固液兩相區(qū)凝固過(guò)程中， 研究了MnBi析出相組織在無(wú)磁場(chǎng)和強(qiáng)磁場(chǎng)條件下的演化過(guò)程。 結(jié)果表明： 在無(wú)磁場(chǎng)條件下MnBi析出相形態(tài)在340℃（MnBi相順磁-鐵磁轉(zhuǎn)變溫度）附近發(fā)生突變， 由較規(guī)則的六方塊狀變?yōu)檠?I>ab面長(zhǎng)大的不規(guī)則片狀； 10T磁場(chǎng)條件下析出相形態(tài)突變的溫度提高到355℃左右。另外， 10T磁場(chǎng)能夠控制析出相晶粒以c軸平行磁場(chǎng)取向、 定向聚合和熔合長(zhǎng)大，使析出相的最終形態(tài)又趨向較規(guī)則的六方塊狀。
關(guān)鍵字: 強(qiáng)磁場(chǎng)； 金屬凝固； 晶體生長(zhǎng)； Bi-Mn合金； 磁性相變
precipitated phase in Bi-Mn alloy solidified from mushy zon
HUANG Hui1,WANG Qiu-liang1, YAN Lu-guang1
（ 1. Institute of E1ectrical Engineering, Chinese Academy of Sciences, Beijing 100080, China;
2. Department of Materials Science and Engineering,
Shanghai University, Shanghai 200072, China）
Abstract: The structural evolution of the MnBi precipitated phase in Bi-6%Mn alloy was experimentally studied with or without a high magnetic field applied during the alloy solidified from the semi-solid zone above 355℃, the magnetic transition temperature of MnBi compound upon heating. In the absence of a magnetic field, it was found that the precipitated phase changed suddenly from a shape similar to its hexagonal single crystal to an irregular oblate shape formed by a rapid growth of the grains along their ab-planes at the temperature near 340℃, the magnetic transition temperature of MnBi compound upon cooling. In the present of a 10T magnetic field, the temperature at which the shape changed abruptly was increased to 355℃ or so. Furthermore, the MnBi grains were controlled by the 10T field to be oriented with their c-axes, directionally aggregated and grown up along the field so that the ultimate shape of the precipitated phase was tend to be regular again.
Key words: high magnetic field; metal solidification; crystal growth; Bi-Mn alloy; magnetic transformation
